27.neurodiagnostics

Question 1

what is a motor unit made up of

Answer 1

1. motor neuron (innervates a lot of myofibril)2. NMJ3. myofibers (homogenous)

Question 2

what is a motor neuron made up of

Answer 2

1. cell body in CNS (ventral horn or CN nuclei)2. peripheral axon supported by Schwann cells

Question 3

ancillary tests for ruling in or out NM dz or LMN dz

Answer 3

1. CK–indicator of skeletal muscle damage2. blood electrolytes, lactate3. urine myoglobin (pigmenturia–RO Hburia w/ammonium sulfate ppt)4. thyroid panel5. Ach receptor Ab (MG)6. 2M antibody titer (masticatory myopathy)7. tick borne titers8. EMG9. muscle nerve bx

Question 4

what is EMG

Answer 4

detection and characterization of electrical activity recorded from a patients muscleslack of abN findings does NOT exclude dzcan aide which tissues to bxabN identified are NOT specificcan ddx btwn dennervation vs disuse atrophy

Question 5

T/FEMG can detect abN in sensory neurons

Answer 5

FALSEEMG can NOT ID disorders restricted to sensory neurons

Question 6

4 types of spontaneous electrical activity on EMG in normal muscle

Answer 6

1. insertional activity (irritation, brief bursts of electrical activity)2. miniature end plate potentials (needle near NMJ, “noise” from ongoing Ach release/depol)3. end plate spikes (single spike from complete depolarization)4. motor unit action potentials (muscle is not at rest and is voluntarily contracting)

Question 7

3 types of abN spontaneous activity on EMG

Answer 7

1. fibrillation potentials and positive sharp waves (spontaneous, hypersensitive bc destabilized sarcolemma)2. complex repetitive discharges (polyphasic, repetitive,uniform frequency, configuration, and waveform)3. myotonic potentials (same as above BUT waxing and waning frequencies)

Question 8

muscles to biopsy

Answer 8

1. lateral head triceps (distal third)2. vastus lateralis (distal third)3. cranial tibial (proximal third)4. temporalis muscle

Question 9

open muscle biopsy technique

Answer 9

parallel to muscle fiber orientation2 cm long incisions separated 0.25 cm and 0.5 cm deepuse special clamps to prevent contracture (remove after 24 hours in fixative)take additional specimen for routine histochemical staining

Question 10

fixative for muscle biopsy

Answer 10

1. specimen for EM done before adding in fixative2. fixative—- glutaraldehyde3. take additional specimen for histochemical routine staining4. should be FROZEN

Question 11

satisfactory nerve to biopsy if generalized disease present

Answer 11

common peroneal nervemixed nerve motor, sensory and autonomic fx